\input pstfig
$
\setcoorunit{4}{1}
\psset{xunit=0.4\psyunit}
%\drawaxes{-2.6}{5}{-3}{3.2}
\drawaxes{-3.5}{4}{-1.4}{2.4}
\markxlabel{0}{\scriptstyle O}{1em}
\uput[-45](0,2){2\pi}
\uput[-45](0,1){\pi}
\uput{1ex}[-180](0, 0.35){\nfrac{\pi}{2}}
\uput[-45](0,-1){-\pi}
%\psset{showpoints=true}
\psplot[algebraic=false]{ 0}{3}{0.5 x 1 atan 180 div sub}
\psplot[algebraic=false]{-3}{-0.0001}{0.5 x 1 atan 180 div sub 2 add}
\thinline
\psplot[algebraic=false]{ 0}{3}{0.5 x 1 atan 180 div sub 1 add}
\psplot[algebraic=false]{-3}{-0.0001}{0.5 x 1 atan 180 div sub 2 add 1 add}
\psplot[algebraic=false]{ 0}{3}{0.5 x 1 atan 180 div sub 1 sub}
\psplot[algebraic=false]{-3}{-0.0001}{0.5 x 1 atan 180 div sub 2 add 1 sub}
\dashline
\psline(-3, -1)(3, -1)
\psline(-3,  1)(3,  1)
\psline(-3,  2)(3,  2)
$
\bye
